
#include<vector>
#include<algorithm>
#include<stack>
#include <climits> 
struct TreeNode
{
    int val;
    TreeNode* left;
    TreeNode* right;

    TreeNode() : val(0), left(nullptr), right(nullptr)
    {
    }

    TreeNode(int x) : val(x), left(nullptr), right(nullptr)
    {
    }

    TreeNode(int x, TreeNode* left, TreeNode* right) : val(x), left(left), right(right)
    {
    }
};
class Solution {
public:
    TreeNode* trimBST(TreeNode* root, int low, int high) {
        if (root == nullptr)
        {
            return nullptr;
        }
        if (root->val < low )
        {
            return trimBST(root->right, low, high);
        }
        if (root->val > high)
        {
            return trimBST(root->left, low, high);
        }
        root->left = trimBST(root->left, low, high);
        root->right = trimBST(root->right, low, high);
        return root;
    }
};
